iPhone 4 16GB GSM proximity sensor and noise mic not working

I have iPhone 4 16GB att that I bought in 2010 so it is out of warranty. Few days ago, power button stopped working. I disassempled the phone and noticed that small part(like tiny dot) on power flex cable that connects with power button was missing. so I bought a new flex cable on ebay for about 5 bucks and replaced it. Now power button clicks and works but this repair raised 2 more issues.

1. proximity sensor not working, screen won't go off when I put phone against the ear.

2. noise cancelling mic not working, no sound when I record video, no sound during call (while using speaker), no sound during facetime, but I can hear the person on the other end.

So I have to use headphone for face time and bottom mic works fine during the call. is it just bad flex and proximity cable.

Additional info:

I tried, reboot, reset network settings, complete factory restore, no luck.

I didn't touch the lcd screen and/or digitizer.

Please help.